1. Technical Field
The present invention relates to a cleaning method and a cleaning device appropriate for an ink jet recording apparatus.
2. Related Art
An ink jet recording apparatus is provided with a cartridge holder and a recording head, and is configured to discharge ink droplets from the recording head corresponding to print data for forming an image on a recording medium such as paper by supplying ink to the recording head through an ink supply path from an ink cartridge which is attached to a cartridge.
In such an ink jet recording apparatus, since a printing test has been performed prior to a product shipment, ink remains in the ink supply path. When ink has been left undone in the ink supply path for a long time, a problem may occur such that a clogging of ink is formed in the recording head.
In order to eliminate ink from the ink supply path, at the time when the printing test has been finished prior to the product shipment, an operation to clean the ink supply path from the cartridge holder to the recording medium is first performed, and then the shipment of the product is made. Cleaning the ink supply path is performed in a manner that a cleaning liquid is introduced to the ink supply path by attaching a cleaning liquid cartridge containing the cleaning liquid to the cartridge holder, or connecting a tube where the cleaning liquid is supplied to the cartridge holder.
Recently, in the large ink jet recording apparatus, since an ink supply path from a cartridge holder to a recording head becomes comparatively greater in length than before, it is necessary to enhance a cleaning efficiency. As a method to enhance the cleaning efficiency, a cleaning method to strengthen a cleaning action has been suggested by mixing air into the cleaning liquid introduced to the ink supply path. For example, JP-A-2003-211702 (see paragraph [0009]) discloses a mixture generating unit which is capable of continuously generating a mixture in which air is mixed with a cleaning liquid, and a cleaning method that introduces the mixture in which air is mixed with the cleaning liquid generated from the mixture generating unit to the ink supply path of a recording apparatus. In addition, JP-A-2010-228297 (see paragraph [0008]) discloses a cleaning unit with a gas-liquid two-phase agent generating unit which generates a gas-liquid two-phase agent by mixing a cleaning liquid and gas, and a gas-liquid two-phase agent supplying unit which is connected to an upstream end in the direction where ink flows in the ink supply tube and supplies the gas-liquid two-phase agent generated by the gas-liquid two-phase agent generating unit to an ink supply tube.
In the cleaning methods as disclosed in JPA-2003-211702 and JP-A-2010-228297, the cleaning liquid in which gas is mixed (hereinafter, it will be referred to as “gas-liquid mixture”) remains in the ink supply path after cleaning. If the recording apparatus is shipped in such a state, when a user installs an ink cartridge and refills ink, an air bubble contained in the cleaning liquid is likely to have been mixed into ink. Printing with ink where an air bubble is mixed causes a pressure loss to occur at the time of discharging the ink. Therefore, a bad quality is likely to be caused such as ink dot omissions due to curved flight of ink droplets or failure of discharging ink droplets.